1. Field of the Invention
The present invention relates to a process for waste treatment, and more particularly to improvements in a process for the removal or elimination of odour from gaseous or liquid effluents containing odorous organic sulphide compounds.
2. Description of the Prior Art
Organic sulphide compounds have acquired a reputation as a class for being evil smelling, noxious and in some cases toxic. Accordingly, in order that effluents may be permitted to be discharged into the environment, it is of public concern that they be removed beforehand from the effluents. Various sub-classes of organic sulphides includes mercaptans, dialkyl sulphides, dialkyl disulphides and thio substituted aryl or alicyclic compounds. Such sulphur compounds can be generated as by-products in a variety of industries, for example, in the paper industry, in which digestion of wood chips in the Kraft process causes malodorous compounds to be present in the resultant black liquors, the condensates from digestion and various wash waters and pulp-bleaching waters. Concentration of the black liquor and its subsequent calcination also produces unacceptable smells. Other industries include the petroleum and gas-refining industries which suffer similarly as a result of the raw feedstock being contaminated with sulphur and sulphides, at least part of which is converted to organic sulphides such as mercaptans during the various crack and fractionating process steps. A further industry is that of animal carcass rendering, which produces a mixture of by-products of which a significant contributor to the offensive smell of them is the class of organic sulphides. In a yet further industry, the organic synthesis of e.g. fungicidal, insecticidal or antibiotic intermediates and vulcanisation of rubber can generate gaseous effluents containing organic sulphides.
It has hitherto been suggested to remove or eliminate organic sulphides by oxidation of them with hydrogen peroxide in an aqueous acidic medium, preferably at pH 3-5 and preferably in the presence of a copper catalyst, as disclosed by Stas et al in U.S. Pat. No. 4,443,342, issued April 1984 and assigned to Interox. Such a process is more effective than the similar use of iron as disclosed in the Effluent and Water Treatment Journal, August 1979, Focus on Interox, but it is not always convenient to employ acidic conditions because mercaptans have only limited solubility in aqueous acidic media and discharge of copper at higher than trace concentrations is also unacceptable.